This invention relates to improvements in a vane pump of a type which is generally well known in the art.
Vane types of pumps are generally provided with a pump housing and a rotor disposed between a pressure plate and a housing body, with the rotor connected to a driving shaft. The rotor has radialy displacable vanes and a surrounding cam ring. Pressure chambers and suction chambers of the pump are formed in the region between the confronting wall surfaces of the housing body and the pressure plate from which pressurized fluid in the pressure chambers is conducted to an outlet in accordance with prior art arrangements as exemplified by the disclosures in U.S. Pat. Nos. 2,357,334, 3,311,064 and 4,416,598 to Kendrick, Eichele and Merz, respectively. Such vane type pumps may also have pressure equalizing passages for the pressure chambers between the pressure plate and front wall of the housing body. The pressure equalization passages were heretofore simple, flat grooves or channels in the front wall of the housing body or in the confronting wall of the pressure plate opposite its pressure side.
Vane type pumps of the foregoing type were prone to the development of noise especially under high speed conditions mainly because of pressure pulsations. For this reason, correspondingly large pressure chambers have been proposed in order to decrease or avoid high magnitude pressure pulsations. However, such corrective measure is inconsistent with the need to construct the pump as small as possible. Further, the pressurized spaces within the pump should be made as small as possible in order to minimize internal forces.
In regard to the latter size reduction measure, the pressure collection space on the pressure side of the pump has been correspondingly enlarged so that the pressure pulsations may be reduced. However, such enlargement of the pressure collecting space is disadvantageous since it involves a significant increase in the size of the pump construction. Furthermore, the degradation of the pressure pulsations thereby achieved, is rather limited.
Therefore, an important object of the present invention is to provide a vane cell pump of the aforementioned type that is less costly to manufacture and yet avoids or largely reduces the pressure pulsations with minimal increase in size of the pump construction.